The person skilled in the art knows the advantages of monolithic technology on gallium arsenide (GaAs) for microwave applications.
However, there is problem with delay lines: in order to obtain the equivalent of a transmission line in air having a length of about 1 centimeter and with an impedance of 50 ohms, the necessary area of GaAs would be about 1 square millimeter.
Such a delay line is not satisfactory since the ratio between the area of GaAs used and the length of the equivalent transmission line in air is very high. This technological problem makes it difficult and expensive to provide such a function on a GaAs substrate.
The aim of the invention is to provide a solution to this problem. To this end, the invention provides a microwave delay circuit designed as an all-pass filter having a phase law which is a linear function of frequency and which is capable, particularly with GaAs technology, of occupying a reduced area by virtue of a special disposition of the essential component parts of the circuit in accordance with the invention.